The change was first spotted today by Matt Buchanan, who saw the Twitter option removed overnight.

The blogging site said it was "truly disappointed" in Twitter's decision.

"To our dismay, Twitter has restricted our users' ability to 'Find Twitter Friends' on Tumblr. Given our history of embracing their platform, this is especially upsetting," Tumblr said in a statement. "Our syndication feature is responsible for hundreds of millions of tweets, and we eagerly enabled Twitter Cards across 70 million blogs and 30 billion posts as one of Twitter's first partners."

Tumblr joins the many sites and developers, including LinkedIn and Instagram, slighted by Twitter's recently announced revised API guidelines. Twitter plans to begin enforcing the guidelines in six months.

Related stories

Twitter declined to comment on Tumblr's change, but when Instagram removed Twitter from its friend-finder for the same reasons, the company released a statement saying, "We understand that there's great value associated with Twitter's follow graph data, and we can confirm that it is no longer available within Instagram."